1. Field of the Invention
The present disclosure relates to semiconductor light emitting elements, and more particularly, to a semiconductor light emitting element with high light extraction efficiency.
2. Description of the Related Art
Light emitting elements using a nitride semiconductor material are known as light emitting elements that are able to emit light within a wide range of wavelengths, from near-ultraviolet light to red light. The general basic structure of the nitride semiconductor light-emitting element includes an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer stacked on an insulating substrate in this order. Further, an n-side electrode for energizing the n-type nitride semiconductor layer and a p-side electrode for energizing the p-type nitride semiconductor layer are formed at an upper surface side of the p-type nitride semiconductor layer.
Electrode structures may affect characteristics of the light emitting element (for example, output, light extraction efficiency, and an element resistance of the light emitting element, and the like). In order to improve the characteristics of the light emitting elements, an electrode structure has been studied from various viewpoints. For example, in the light emitting element having an upper surface of the p-type nitride semiconductor layer serving as a light emitting surface, the metal electrode formed on the light emitting surface functions as a light shielding member and therefore the light extraction efficiency will be reduced. Particularly, when both the n-side electrode and the p-side electrode are provided with an extending electrode made of metal in order to diffuse current into the entire light emitting element, the extending electrode also serves as the light shielding member and therefore the light extraction efficiency will be further reduced.
To address this problem, Japanese Patent Application No. JP 2012-114343 A discloses an electrode wiring in which a p-side electrode and an n-side electrode (mainly, extending electrodes thereof) are stacked via an insulating layer so that these electrodes partially overlap with each other as viewed from the light emitting surface side. Partial overlapping of these electrodes leads to a reduction of a light shielding area shielded by the electrodes as compared to an electrode wiring without overlap. As a result, the light extraction efficiency can be enhanced.
According to JP 2012-114343 A, an insulating film is provided between the electrodes and semiconductor layers, and each electrode is in electrical conduction with the corresponding semiconductor layer through a plurality of penetrating electrodes. However, since the n-side electrode and the p-side electrode overlap with each other so as to reduce the light shielding area, it is difficult to connect each electrode to the penetrating electrodes. For this reason, each electrode is provided with a plurality of protrusions extending in a plane parallel to the light emitting surface in order to connect each electrode to the penetrating electrodes through the protrusions. The protrusions of the n-side electrode and the protrusions of the p-side electrode are arranged so as to not overlap with each other as viewed from the light emitting surface side.